@@ -35,7 +35,8 @@ typedef struct {

 typedef struct {

 	Uint8 data[LENGTH];

-	Uint16 ptr, length, llen, mlen, rlen;

+	unsigned int ptr, length;

+	Uint16 llen, mlen, rlen;

 	Label labels[512];

 	Macro macros[256];

 	Reference refs[2048];

@@ -193,6 +194,10 @@ writebyte(Uint8 b)

 		fprintf(stderr, "-- Writing in zero-page: %02x\n", b);

 		return 0;

 	}

+	else if(p.ptr > 0xffff) {

+		fprintf(stderr, "-- Writing after the end of RAM: %02x\n", b);

+		return 0;

+	}

 	else if(p.ptr < p.length) {

 		fprintf(stderr, "-- Memory overwrite: %04x -> %04x\n", p.length, p.ptr);

 		return 0;